Sorting multi-dimensional array by count of subarray - php

Question

I have the array like this:
Array
(
[28748] => stdClass Object
(
[uid] => 28748
[status] => 1
[children] => Array
(
[29163] => stdClass Object
(
[uid] => 29163
[status] => 1
)
)
)
[28708] => stdClass Object
(
[uid] => 28708
[status] => 1
[children] => Array
(
[27104] => stdClass Object
(
[uid] => 27104
[status] => 1
[children] => Array
(
[28250] => stdClass Object
(
[uid] => 28250
[status] => 1
)
)
)
[29448] => stdClass Object
(
[uid] => 29448
[status] => 1
[children] => Array
(
[28528] => stdClass Object
(
[uid] => 28528
[status] => 1
)
[28329] => stdClass Object
(
[uid] => 28329
[status] => 1
[children] => Array
(
[28533] => stdClass Object
(
[uid] => 28533
[status] => 1
)
)
[26548] => stdClass Object
(
[uid] => 26548
[status] => 1
)
)
)
)
)
)
And I want to sort the array by the count of sub array, so the no of children is greater will come first. The level of dimension is unlimited. In my case I want to become this array:
Array
(
[28708] => stdClass Object
(
[uid] => 28708
[status] => 1
[children] => Array
(
[29448] => stdClass Object
(
[uid] => 29448
[status] => 1
[children] => Array
(
[28329] => stdClass Object
(
[uid] => 28329
[status] => 1
[children] => Array
(
[28533] => stdClass Object
(
[uid] => 28533
[status] => 1
)
)
[28528] => stdClass Object
(
[uid] => 28528
[status] => 1
)
[26548] => stdClass Object
(
[uid] => 26548
[status] => 1
)
)
)
[27104] => stdClass Object
(
[uid] => 27104
[status] => 1
[children] => Array
(
[28250] => stdClass Object
(
[uid] => 28250
[status] => 1
)
)
)
)
)
[28748] => stdClass Object
(
[uid] => 28748
[status] => 1
[children] => Array
(
[29163] => stdClass Object
(
[uid] => 29163
[status] => 1
)
)
)
)
Here is the new array that i am checking:
Array
(
[27104] => stdClass Object
(
[uid] => 27104
[status] => 1
[children] => Array
(
[28250] => stdClass Object
(
[uid] => 28250
[status] => 1
[children] => Array
(
[28839] => stdClass Object
(
[uid] => 28839
[status] => 1
[children] => Array
(
[27102] => stdClass Object
(
[uid] => 27102
[status] => 1
)
)
)
)
)
[26551] => stdClass Object
(
[uid] => 26551
[status] => 1
[children] => Array
(
[25368] => stdClass Object
(
[uid] => 25368
[status] => 1
)
)
)
)
)
[28708] => stdClass Object
(
[uid] => 28708
[status] => 1
[children] => Array
(
[29448] => stdClass Object
(
[uid] => 29448
[status] => 1
[children] => Array
(
[28528] => stdClass Object
(
[uid] => 28528
[status] => 1
)
[28329] => stdClass Object
(
[uid] => 28329
[status] => 1
[children] => Array
(
[28654] => stdClass Object
(
[uid] => 28654
[status] => 1
)
)
)
[26548] => stdClass Object
(
[uid] => 26548
[status] => 1
)
)
)
)
)
[28748] => stdClass Object
(
[uid] => 28748
[status] => 1
[children] => Array
(
[28838] => stdClass Object
(
[uid] => 28838
[status] => 1
)
[28685] => stdClass Object
(
[uid] => 28685
[status] => 1
)
[29163] => stdClass Object
(
[uid] => 29163
[status] => 1
)
)
)
)
and after using "sortByNumChildren($data)" i'm getting
Array
(
[28748] => stdClass Object
(
[uid] => 28748
[status] => 1
[children] => Array
(
[29163] => stdClass Object
(
[uid] => 29163
[status] => 1
)
[28685] => stdClass Object
(
[uid] => 28685
[status] => 1
)
[28838] => stdClass Object
(
[uid] => 28838
[status] => 1
)
)
)
[28708] => stdClass Object
(
[uid] => 28708
[status] => 1
[children] => Array
(
[29448] => stdClass Object
(
[uid] => 29448
[status] => 1
[children] => Array
(
[26548] => stdClass Object
(
[uid] => 26548
[status] => 1
)
[28329] => stdClass Object
(
[uid] => 28329
[status] => 1
[children] => Array
(
[28654] => stdClass Object
(
[uid] => 28654
[status] => 1
)
)
)
[28528] => stdClass Object
(
[uid] => 28528
[status] => 1
)
)
)
)
)
[27104] => stdClass Object
(
[uid] => 27104
[status] => 1
[children] => Array
(
[26551] => stdClass Object
(
[uid] => 26551
[status] => 1
[children] => Array
(
[25368] => stdClass Object
(
[uid] => 25368
[status] => 1
)
)
)
[28250] => stdClass Object
(
[uid] => 28250
[status] => 1
[children] => Array
(
[28839] => stdClass Object
(
[uid] => 28839
[status] => 1
[children] => Array
(
[27102] => stdClass Object
(
[uid] => 27102
[status] => 1
)
)
)
)
)
)
)
)
and this looks incorrect as this is not sorted by all children's count.
sorting should be according to the number of all descendants.
Please check this.

Answer 1

thank you so much for your answer #trincot .
but i think one thing i missed here
if the total number of children is greater then that array will come first.
As mentioned in my array suppose i have added 2 more elements in the first sub array likewise
28748 => stdClass Object
(
[uid] => 28748
[status] => 1
[children] => Array
(
[29163] => stdClass Object
(
[uid] => 29163
[status] => 1
)
[29173] => stdClass Object
(
[uid] => 29173
[status] => 1
)
[29174] => stdClass Object
(
[uid] => 29174
[status] => 1
)
)
)
total no of children in first sub array = 3
total no of children in second sub array = 7
but total no of children(counting inner children as well) in the second sub array is greater so the second sub array will come first and this shold work same as in the inner part as well.
Please look into this.

Answer 2

You could use a recursive function that sorts each level with uasort:
function sortByNumChildren(&$array) {
foreach ($array as $key => &$obj) {
if (isset($obj->children)) sortByNumChildren($obj->children);
}
uasort($array, function ($a, $b) {
if (!isset($a->children)) return 1;
if (!isset($b->children)) return -1;
return count($b->children) - count($a->children);
});
}
Call this function as follows:
sortByNumChildren($data);
See it run, together with output, on eval.in
This code will sort by number of (immediate) children. See below for sorting on number of descendants.
Code for sorting by number of all descendants
As requested here is an alternative piece of code which sorts the nested array by number of descendants, so also counting grandchildren and their children, etc.:
function sortByNumChildren(&$array) {
$childCounts = array();
foreach ($array as &$obj) {
$childCounts[$obj->uid] = isset($obj->children) ?
sortByNumChildren($obj->children) : 0;
}
uasort($array, function ($a, $b) use ($childCounts) {
return $childCounts[$b->uid] - $childCounts[$a->uid];
});
return count($array) + array_sum($childCounts);
}
Call this function as follows:
sortByNumChildren($data);
See it run, together with output, on eval.in